Silicon wafers used in semiconductor integrated circuit fabrication typically undergo numerous processing steps, including deposition, patterning, and etching steps. In each manufacturing step, it is often necessary or desirable to modify or refine an exposed surface of the wafer in order to prepare the wafer for subsequent fabrication or manufacturing steps. For example, semiconductor wafers having shallow trench isolation (STI) structures require planarization of the dielectric material prior to further processing.
One method of modifying or refining exposed surfaces of wafers employs a continuous process that treats a wafer surface with a polishing slurry containing a plurality of loose abrasive particles dispersed in a liquid. Typically this slurry is applied to a polishing pad and the wafer surface is then ground or moved against the pad in order to remove material from the wafer surface. Generally, the slurry also contains agents that chemically react with the wafer surface. This type of process is commonly referred to as a chemical-mechanical polishing (CMP) process.
Over time, the surface of the polishing pad becomes glazed with entrained by-products of the polishing process, thereby decreasing the removal rate or polishing uniformity for subsequent wafers. In order to maintain the condition of the polishing pad over time, the pad is periodically exposed to a pad conditioner having an industrial diamond surface, and rotated at a specified speed to roughen the polishing pad surface. The CMP pad conditioning process must be carefully monitored in order to maintain a desired wafer surface topography.